Revert "Simplified boost::compute interaction"
Revert "Simplified boost::compute interaction"

This reverts commit 0e6527fa943d1270b30fa71b575014b0ce54dc46.

boost::compute::buffer_iterator does not own its buffer after all.

Poulpy21/vexcl,ddemidov/vexcl,Poulpy21/vexcl,kapadia/vexcl,Poulpy21/vexcl,ddemidov/vexcl,kapadia/vexcl